1. Field of the Invention
The present invention relates to an oil filter to be incorporated in a lubricating system for an internal combustion engine or the like and, more particularly, to an oil filter of a type in which not only solid contaminants 1 but also gaseous contaminants can be removed from the oil.
2. Description of the Prior Art
In machinery for construction, transportation and the like using lubricant, such as engines and various hydraulic devices, solid contaminants and gaseous contaminants have hitherto been removed from lubricant by separate devices and/or in different portions of the machinery. An integrated device has thus been desired which can remove both of the solid and gaseous contaminants effectively and which can be installed in a limited space of the machinery.
The inventors herein have proposed such an integrated device in a pending Japanese Patent Application No. 202682/88 filed Aug. 16, 1988. The device disclosed therein comprises a first separator for filtering lubricant which is pumped into a housing to thereby remove solid contaminants, and a second separator for removing gaseous contaminants from the filtered oil by utilizing a centrifugal force. Specifically, the second separator has a chamber adapted to generate a vortical flow of the lubricant introduced therein, whereby the lubricant having little gaseous contaminants and therefore having a larger specific gravity gathers in a peripheral area of the chamber while gas-rich lubricant having a smaller specific gravity gathers in a central area. A wall defining the chamber is provided with a plurality of pores through which the gas-removed lubricant flows out of the chamber. On the other hand, the gas-rich lubricant is discharged by a perforated pipe which extends into the chamber along its axis.
In the above proposed device, the second separator projects in the axial direction beyond the first separator unit. Therefore, the axial length of the device must be sufficiently larger than that of each separator, resulting in a difficulty in designing the device to be installed in a small space without spoiling the removal efficiency of contaminants. Further, to incorporate the device into a lubricating system necessarily involves attaching it to a mount in which various passages should be provided to supply the lubricant into the device, lead the filtered and gas-removed lubricant to various parts to be lubricated, and to discharge the gas-rich lubricant into a tank for recirculation. The above device is not so constructed that it may easily be attached to the mount, and a relatively complicated work will be needed for the attachment.